Would You Drive a Stop-Start Vehicle in 2014?

So, what do you know about stop-start technology? Ever driven a stop-start car?

MADISON, Wis. – So, what do you know about stop-start technology? Ever driven a stop-start car?

Probably not. Neither have I. But a recent conversation with Cecilia Smith at Texas Instruments got me interested. Smith is vice president of the Mixed Signal Automotive (MSA) part of TI’s High Volume Analog and Logic business.

The idea behind stop-start seems quite straightforward. The system automatically switches off the engine when the car is at a standstill and restarts it as soon as the driver presses the clutch pedal or releases the brake.

Imagine your car stuck in a traffic jam or waiting at a traffic light. The ability of a vehicle to automatically stop its engine when stationary and then fire up again when it’s time to move could lead to significant fuel savings and reduction in vehicle emissions, according to Navigant Research.

Stop-start vehicles, in fact, might be finally coming our way, in volume, over the next several years. In its recent report Navigant Research forecasts that total global sales for light-duty stop-start vehicles will exceed 55 million by 2022, accounting for 54.3% of total vehicle sales.

Of course, today the reality is much different.

The stop-start market share in the United States in 2012 was one percent, compared to Europe’s double-digit percentage, according to a report by SAE International, formerly the Society of Automotive Engineers.

So, what’s stopping carmakers from going big on stop-start vehicles -- especially in the United States?

One nagging issue is the lag time between stop and start. Carmakers are worried that driver impatience (or the Jackrabbit Syndrome) might just kill the US consumers’ appetite for stop-start technology.

A case in point is a Honda’s decision earlier this year. The Japanese carmaker decided to drop stop-start technology for the US market in its Honda Fit when it’s launched in the US market in 2014.

I'm glad you commented on your real-world experience. I was wondering specifically about this vehicle. I suspect it's much more representative of what we would expect. In concept, it sounds great to start movement with a big electric starter while the gas engine is starting up. However, the need for immediate power can overwhelm it on occasion.

Back when early electronic fuel injection came along, I noticed a delay between hitting the accelerator and the engine reving up. With a carburator, the accelerator pump would squirt extra gas in as the pedal was pressed, causing immediate response. However, with the first throttle body fuel injection I drove, you press the accelerator, alowing more air in. After that air passes through the engine, the oxygen sensor would detect an overly lean mixture and then add more gas.

That delay, though quite short, was enough to cause a concern now and then similar to your Silverado concern. Even a half a second can be quite unnerving in a setting you described.

I used to drive a 2009 Chevy Silverado hybrid pickup and my wife currently drives a 2012 Prius, both of which stop the engine when the vehicle stops (assuming certain conditions such as engine is warmed up, battery is sufficiently charged, etc.)

The Silverado being such a heavy vehicle (5000+ lbs) with a large V8 engine is more similar to a start-stop vehicle than the Prius. Even though the Silverado had a 300 volt battery driving a powerful starter motor, there was a noticable delay when transitioning from stop to start. On more than one occasion, as I pulled onto a rural highway not far from a blind curve, an 18-wheeler abruptly appeared from around the curve necessitating immediate action on my part. With the gas pedal on the floor, I could almost count the milliseconds while waiting for the engine to start. (The Prius is far more frightening in this situation since the engine is very small by comparison.)

Admittedly, this would not happen with a start-stop vehicle since the car wouldn't be driving into the busy highway before the engine started. But I can imagine a situation where such acceleration would be necessary from a complete stop.

With a manual transmission, I assume it would be less noticable since the driver is more in control of when the engine starts (by depressing the clutch). But what about an automatic? If an emergency situation requires immediate power, will the gas pedal be on the floor before the engine has had time to start?

<<Of course, knowing that your engine will shut down if you miss the green means more people will try to outrun them>>

I've been driving one for over 2 years. It only shuts down if I put it in neutral; if I sit with my foot on the clutch, it doesn't. So, it's my choice whether to shut it down or not. If I decide to shut it down, it takes as long as it takes to press the clutch and put it in first (0.5 seconds?), which is probably less time than the red and amber and as I'm not am amber gambler...

The problem isn't just waisted fuel while stopped, it's more the energy that is waisted in braking. Many of the problems raised with the start/stop technology have to be addressed with hybrid as well. This certainly applies to heating, cooling and maintaining proper engine temperature.

It would make sense to drive air conditioning compressor with electric motor run off the same battery system as traction motors. Any heating not immediately available from engine should be derived from directly oxidizing some of the fuel.